The present invention relates to a transmission apparatus used in controlled equipment such as industrial robots which can reverse the rotating direction during operation.
In the controlled equipment such as industrial robots, the power shaft is not driven in one direction only but its rotating direction is reversed during operation. The gears in the transmission apparatus incorporated in such controlled equipment always have backlash and the existence of the backlash delays the reversing action of the output shaft to the extent corresponding to the backlash, resulting in the power transmission becoming inaccurate. This problem has long been pointed out in the industry.
To eliminate such power transmission inaccuracy due to backlash, it has been proposed that two gears are put together with their phases shifted to such an extent corresponding to the backlash to make these two gears engage with a mating gear without any backlash. However, the backlash is produced partly by an unavoidable machining error and, considering the limit in improving the machining accuracy, it is extremely difficult to shift the two gears' phases exactly corresponding to such a minute backlash and fix them to the shaft.
Furthermore, the above double gear mechanism cannot avoid a wedge effect inherent to the two teeth engagement structure, making a smooth operation of the transmission difficult.